Plastisols are, in general terms, visco-elastic materials prepared from a major portion of a plasticizer and a minor portion of a resin. Such visco-elastic or plastisols are dispersions of special fine particle size polyvinylchloride resins in plasticizing liquids. In addition to the resins and plasticizers, heat stabilizers and color pigments may be added. In general, plastisol is liquid at room temperature and, upon heating, fusion takes place and the plastisol is converted into a tough, homogeneous mass with excellent abrasion and impact resistance. An example of one such material is discussed in U.S. Pat. No. 4,756,949 issued Jul. 12, 1988 to Spence, et al.
The material described in the '949 patent has been utilized in the formation of pads or cushions for use with bicycle seats. In that application, the plastisol has been fused and is contained within a relatively heavy and cumbersome cover by which it is attached to the bicycle seat. Also, the cover must be maintained carefully because the plastisol is not encapsulated and, thus, is subject to bleeding of plasticizers from the plastisol. In the event that such plasticizers escape from the pad, damage to the clothing worn by the rider of the bicycle may occur.
An object of this invention is to provide a shock absorbing and cushioning pad that is formed from a fused plastisol which is in turn encapsulated within a very flexible, deformable and elastic material which is impermeable to the plasticizers contained within the plastisol.
Another object is to provide a shock absorbing cushioning pad assembly for use on bicycles or the like that includes, in addition to the plastisol pad mentioned above, an elastic cover that is arranged to secure the pad to a bicycle seat or the like.
A further object of the invention is to provide a method for making a fused plastisol pad that is totally encapsulated to prevent the loss of plasticizers therefrom when the pad is in use.